1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to solid golf balls having a core and a cover.
2. Description of the Related Art
In recent years, three-piece golf balls were developed in attempts to accomplish a feel at impact that is comparative to wound balls, and have been supplied on the market. JP-A No. 2000-70408 (U.S. Pat. No. 6,299,511) and JP-A No. 2003-52855 (US 2003-40378A1) disclose three-piece golf balls having a mid layer that includes a thermoplastic elastomer.
Golf balls have numerous dimples on the surface thereof. In general, golf balls have single radius dimples having a cross-sectional shape with single curvature radius, or double radius dimples having a cross-sectional shape with two curvature radii. The dimples disrupt the air flow around the golf ball during flight to cause turbulent flow separation. By causing the turbulent flow separation, separating points of the air from the golf ball shift backwards leading to the reduction of a drag. The turbulent flow separation promotes the displacement of the separating point on the upper side and the separating point on the lower side of the golf ball, which results from the backspin, thereby enhancing the lift force that acts upon the golf ball. Reduction of drag and improvement of lift force is referred to as a “dimple effect”. Excellent dimples disturb the air flow more efficiently.
A variety of proposals with respect to the cross-sectional shape of the dimples in attempts to improve flight performances have been made. JP-A No. H05-96026 (U.S. Pat. No. 5,338,039) discloses dimples having a shape with the gradient of a slope disposed in the vicinity of the edge being greater than that of a slope at the bottom part. JP-A No. H09-70449 (U.S. Pat. No. 5,735,757) discloses dimples having a cross-sectional shape given by double radius. JP-A No. 2004-166725 (U.S. Pat. No. 6,899,643) discloses dimples having a great ratio of the curvature radius of the bottom part to the curvature radius in the vicinity of the edge.
With respect to matching of the dimples and the structure, a variety of proposals have been made. JP-A No. 2003-199846 (U.S. Pat. No. 6,659,888) discloses a golf ball having a soft mid layer, and having dimples improved with respect to the contour length.
Top concern to golf players for golf balls is the flight distance. In general, golf balls that are excellent in resilience performances are excellent in the flight performance. However, insufficient feel at impact may be experienced according to golf balls on which only the resilience performance was considered. An object of the present invention is to provide a golf ball that is excellent in the flight performance and feel at impact.